Primary Cutaneous Follicular Helper T-Cell Lymphoma: A Case Series and Review of the Literature.

Primary cutaneous follicular helper T-cell (Tfh) lymphoma is a recently described variant of peripheral T-cell lymphoma-not otherwise specified. This particular variant, usually presenting as a sudden onset of multiple plaques and nodules, is characterized by tumoral atypical T cells that express an array of Tfh markers, such as inducible T-cell costimulator, Bcl-6, CXCL13, PD-1, and CD10. The authors now present 3 patients whose known clinical skin findings are consistent with PTCL of Tfh origin (PTCL-Tfh). The typically protracted pattern of skin disease manifesting as scaly patches and plaques encountered in mycosis fungoides was not seen in our 3 cases, and there were distinguishing light microscopic and phenotypic features. These cases are similar to the few previous reported cases of PTCL-Tfh, although systemic involvement was not seen. The categorization of additional patients into this PTCL subtype in the medical literature would be needed to further characterize this new entity and may lead to better targeted treatments based on specific T-cell subtypes.